Communications traffic at network edges is increasing over time due to the rising demand for a range of high-bandwidth services by business and residential customers. This rising demand places an increasing requirement on access networks to deliver those services.
One type of access network is a Passive Optical Network (PON). A PON typically has a central office (CO) at which apparatus called an Optical Line Termination (OLT) interfaces with a metro or carrier network. An arrangement of optical fibres and splitters connect the OLT with multiple Optical Network Termination units (ONTs). An ONT can be located at a subscriber premises in a Fibre To The Home (FTTH) system, or an ONT can be located at a roadside cabinet near to a group of premises in a Fibre To The Curb (FTTC) system. A PON is so-called because the optical transmission has no power requirements, or limited power requirements, once an optical signal is travelling through the network section connecting the ONT to the OLT.
Existing PONs are based on Asynchronous Transfer Mode Passive Optical Network (APON), Broadband PON (BPON), Gigagbit PON (GPON) and Ethernet PON (EPON) technologies as standardised by the International Telecommunications Union (ITU-T) and Institute of Electrical and Electronic Engineers (IEEE). Many of these PON technologies use some form of time division multiple access technique, with the capacity of a wavelength channel being shared in a time-divided manner across multiple ONTs.
More recently, Wavelength Division Multiplexed Passive Optical Networks (WDM PON) have been proposed. A WDM PON supports multiple wavelength channels. A separate wavelength can be allocated for communication between the Optical Network Unit (OLT) and each ONT in the PON.
In many cases an access network will already be deployed with an operator, called the incumbent operator, owning and operating the access network. In open markets, such as Europe, there is a regulatory requirement that a subscriber should be able to choose between a number of possible operators to provide their communications service. There is a problem of how to allow Other Local Operators (OLOs) to access the existing access network. This complicates the network equipment that must be provided, as an access network must be able to connect to one of a set of operator networks, as required by a subscriber.